Correct Answer: (D)
Explanation: The conclusion is that the marsupial lions must have needed to climb their mother's pouch. Lets consider the choices one by one:
(A) For ancient marsupial lions, firstly, it is nowhere mentioned in the argument that they were born after a short gestation period. May be they were born with only fore limbs developed even after a long gestation period. Secondly, we don't need to assume that they were born with some parts underdeveloped as this is mentioned in the argument itself.
(B) Well developed forelimbs could well have been more advantageous than hind limbs to marsupial lions but for what purpose? May be for running but not necessarily for climbing their mother's pouch. Even if we assume that fore limbs were more advantageous, we cannot say that they were more advantageous for the purpose of climbing.
(C) It is clearly mentioned in the argument that it is an hypothesis that newborn marsupial lions must also have needed to climb into their mothers’ pouches. Paleontologists have no way to determine whether the marsupial lions actually did so or not.
(D) Lets assume that marsupial lions were born with their fore limbs AND hind limbs developed. Logically speaking, they must have been equally capable, if not more, of climbing their mother's pouch. But in the argument, the conclusion is based upon the development of ONLY the front limbs. So to reach the conclusion based upon the development of ONLY the front limbs, it is imperative to assume that the development of hind limbs must have reduced the capability of marsupial lions to climb into their mother's pouch.
(E) Again, the development of only the forelimbs could have been due to some purpose use but simply assuming this is not enough to conclude that the purpose was to climb into their mother's pouch.
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